Paul Coudray

Spectroscopic characterization of intrinsic losses in an organic–inorganic hybrid waveguide synthesized by the sol–gel process

Abstract A promising way of fabricating integrated optics components is based on the sol–gel synthesis and photocuring of hybrid materials. However, the presence of OH groups in these materials is a major factor in optical amplification inhibition. In particular, high losses at 1550 nm are mainly due to non-condensed OH groups originating from the sol–gel process at low temperature. Thus, improvement of the final properties of these materials is correlated with the inhibition of OH group concentration. In this study, we used 29 Si NMR and near infrared spectroscopy to demonstrate the catalytic effect of zirconium (IV) n -propoxide on the condensation reactions of silanol groups. 29 Si NMR showed the absence of silanol species at the end of the synthesis. This result is attributed to the zirconate hydrophilic effect which consumes OH groups by catalysing the polycondensation of Si–OH bonds. In parallel, near-infrared experiments showed the presence of a high proportion of OH species at the end of the synthesis showing that the remaining OH groups are only present in the zirconium species.

Active erbium-doped organic–inorganic waveguide

Abstract The existence of optical amplification at 1550 nm wavelength in channel waveguides using erbium doping and 980 nm laser pump involves as low a OH group quantity as possible. Moreover, a high refractive index variation between the guide and the cladding is necessary to induce a maximum confinement and then increase the doping efficiency. This field is now limited to pure inorganic materials or semiconductors. We propose to extend this field to hybrid organic–inorganic materials. In such a way, we have developed a new composition based on hydrophobic sol–gel precursors to reduce the OH quantity, and on a diacrylate monomer whose reactivity allows a high refractive index change under UV light exposure. Signal enhancement is observed for the first time in a hybrid organic–inorganic channel waveguide.

Sol-gel channel waveguide on silicon: fast direct imprinting and low cost fabrication

Abstract Development of integrated optical devices depends on the possibility to realize them for the lowest cost. In this paper we present an improved technique based on the sol-gel process enabling to fabricate low loss (

Photocurable Sol-Gel Coatings: Channel Waveguides for Use at 1.55 μm

The development and characterization of channel waveguides using wet-process, low temperature sol-gel chemistry is described. Two structures have been developed. The first one is a one-layer structure, composed of a sol-gel solution which is a mixture of photopolymerizable organosilicate and organozirconate precursors. The other is a multilayer structure with a buffer under the guide and a protective coating. The layers are deposited by the dipping technique. The devices are obtained by UV light exposure of the coating through a predefined mask (channel waveguides). The refractive index increase is sufficient enough to allow the use of waveguides in the 1.55 μm telecommunication window.These waveguides are thick enough to reduce the coupling losses with an optical fiber below 0.5 dB. Also, because of our sandwich structure, the propagation losses are less than 0.1 dB.

Integrated optics based on organo-mineral materials

Abstract New technologies based on organic–inorganic materials are shown to be very flexible, while they present interesting performance. The process needs only four steps, and the local refractive index change necessary to guide the light may be imprinted with a simple UV exposure. Several solutions are given to design basic structure of guides and hence to make optical circuits which cover the domain of power splitters to wavelength division multiplexers, including directional couplers, gratings, etc. Optical amplification is also shown to be possible, and the connection problem is tackled.

Direct printing of gratings on sol-gel layers

The sol-gel process is an interesting alternative for making glass integrated-optics components. Reasonable performance can be reached with low-cost fabrication. We show a one-step method for imprinting gratings on a thin layer made through the sol-gel process, thus enlarging the field of application in integrated optics to filters, out-ofplane connections, etc. The efficiency of the grating is studied through diffraction measures and computations.

WDM based on multimode interference-coupler built in an organic-inorganic material

Abstract The WDM phasar, which is a key element in optical telecommunication systems, is shown here to be made with a very low cost and promising technology based on organic–inorganic material, and with a design based on MMI devices for the splitter and the combiner instead of star couplers or gratings. A realization of a first 4×4 MMI phasar, for use around 1.55 μm wavelength, demonstrates the application of these two specific aspects. Experimental measurements and theoretical results are compared.

Wavelength and temperature dispersion of refractive index of thin films

The m-lines guided mode technique is demonstrated as a powerful tool for the measurement of wavelength and temperature refractive index dispersion in thin films. The proper treatment of results reveals measurement uncertainties of the order of 10-3 for the refractive index, and a sensitivity to changes in this quantity of the order 10-6. Furthermore, the thickness of the films can be established to a precision of 1nm. Using an optical stack consisting of a silicon wafer substrate, a low index buffer layer (index 1.52), topped with a polymer blend guiding film, The wavelength dispersion of the change of refractive index of the guiding film with temperature has been successfully measured. The temperature dispersion of the refractive index of the guiding layer is of ~ -6.7×10-5 /K.

Integrated polarization converter made of sputtered inorganic Ta205 and silica sol-gel thin films

A ridge waveguide technology, exhibiting high polarization dependency, is developed to fabricate a new efficient multi-section passive polarization rotator. Theoretical polarization conversion efficiency of 98% at 1.55 µm is expected with excess losses below 0.1dB.